Aim of the Study: To study the relationship of delirium motor subtypes with cognitive and non-cognitive symptoms of delirium in geriatric patients referred to consultation-liaison psychiatry services.Materials and Methods: Ninety eight (N = 98) consecutive patients (aged ≥60 years) with diagnosis of delirium as per DSM-IV TR were rated on Delirium Rating scale-Revised-98 version (DRS-R-98) and amended Delirium motor symptom scale (DMSS).Results: On amended DMSS, hyperactive subtype (N = 45; 45.9%) was the most common motoric subtype of delirium, followed by hypoactive subtype (N = 23; 23.5%), and mixed subtype (N = 21; 21.4%). On DRS-R-98, all patients fulfilled the criteria of 'acute (temporal) onset of symptoms', 'presence of an underlying physical disorder' and 'difficulty in attention'. In the total sample, >90% of the patients had disturbances in sleep-wake cycle, orientation and fluctuation of symptoms. The least common symptoms were delusions, visuospatial disturbances and motor retardation. When compared to hypoactive group, significantly higher proportion of patients with hyperactive subtype had delusions, perceptual disturbances, and motor agitation. Whereas, compared to hyperactive subtype, significantly higher proportion of patients with hypoactive subtype had thought process abnormality and motor retardation. When the hyperactive and mixed motoric subtype groups were compared, patients with mixed subtype group had significantly higher prevalence of thought process abnormality and motor retardation. Comparison of hypoactive and mixed subtype revealed significant differences in the frequency of perceptual disturbances, delusions and motor agitation and all these symptoms being found more commonly in patients with the mixed subtype. Severity of symptoms were found to be significantly different across the various motoric subtypes for some of the non-cognitive symptoms, but significant differences were not seen for the cognitive symptoms as assessed on DRS-R-98.Conclusion: In elderly patients, motor subtypes of delirium differ from each other on non-cognitive symptom profile in terms of frequency and severity.

Delirium is a neuropsychiatric syndrome that typically occurs in the setting of a medical condition and has an acute onset and a transient, fluctuating and reversible course. Studies from the West suggest that delirium is highly prevalent in elderly population with prevalence rates ranging from 15-62% in post-operative period to 70 to 87% in intensive care unit patients. [1],[2] In elderly, delirium is associated with poor outcomes irrespective of baseline characteristics and etiological factors. [2] Delirium contributes to faster cognitive decline, [2] and increase in nursing time, per-day hospital cost, length of hospital stay, [2],[3] institutionalization and death, independent of age, sex, comorbid illness or illness severity, and baseline dementia. [4] Many studies from the West [5],[6] and occasional studies from India [7] have tried to study the clinical features of delirium in elderly. However, very few studies have studied the motor subtypes of delirium and the relationship of the same with other symptoms. [8],[9]

For the last 30 years, there have been attempts to subtype delirium. In one of the first description of subtyping, Lipowski [10] suggested 'hyperactive' and 'hypoactive' subtypes, and later added a third category of 'mixed' in recognition of the fact that many patients experienced elements of both 'hyperactive' and 'hypoactive' subtypes within a short time frame. [11] Later some of the authors have added another subtype, i.e, 'no or neither' subtype to the above three subtypes. [12],[13]

One of the major problems of the subtyping has been the heterogeneity in defining the same. Studies have used the descriptions of agitation and retardation from different rating scales, [14],[15],[16],[17],[18],[19],[20] besides the use of visual analog scales [20] and clinical observation. [21] Although, problematic, but these studies suggest that various motoric subgroups of delirium differ from each other in terms of non-motor symptoms, detection rates, duration of delirium, associated etiologies, treatment experience, and outcome. [22] It has also been shown that core elements of delirium in the form of degrees of cognitive deficits is shared by all the subtypes. [20],[23],[24] However, the earlier studies which evaluated cognitive impairment had done so by using delirium rating scale, which had only one item for assessment of all the cognitive domains. [13] One study used mini-mental status examination (MMSE) scores [20] and reported no difference in the cognitive functions between hyper and hypoactive subtypes. With regard to other symptoms, there is lack of consensus. [16],[25]

It has been suggested that some of the differences in incidence and clinical profile of motor subtypes can be attributed to assessment methods and populations studied. To overcome this limitation, Delirium Motor Subtype Scale (DMSS) was developed by Meagher et al. [27],[28] which has been found to have good concurrent and predictive validity. [27],[28],[29] DMSS was recently amended at our centre and 2 more items were added to the original DMSS to increase the generalizability. [30]

Meagher et al. [24] subtyped delirium and found that compared to patients with hyperactive subtype, patients with hypoactive delirium have lower scores for delusions, mood lability, sleep-wake cycle disturbances, and variability of symptoms. However, the three groups did not differ on cognitive functions. In another study, Meagher et al. [27] by using DMSS reported that mixed subtype patients had more severe sleep-wake cycle disturbance, disorientation and overall symptom fluctuation whereas hyperactive delirium was shorter and more reversible. It has recently also been shown that various subtypes of delirium are stable within delirium episodes in 62% of patients. In the same study the authors reported that the DRS-R98 non-cognitive subscale scores differed across groups whereas cognitive subscale scores did not. [31] These studies are limited to palliative care population.

As there are very few studies which have evaluated motor subtypes of delirium using a specific instrument like DMSS, there is a need to evaluate the characteristics of various motoric subtypes of delirium across different treatment settings. Therefore, the present study aimed to examine the relationship of delirium motor subtypes with other symptoms of delirium using amended DMSS in geriatric patients.

Materials and methods

The study was done at the Postgraduate Institute of Medical Education and Research, Chandigarh, a multispecialty teaching hospital in North India.

The study was approved by the Ethics Review Committee of the Institute and patients were recruited after obtaining written consent from the primary caregivers of the patients.

A prospective study design was followed. Patients admitted to various medico-surgical and emergency wards and found to have delirium by the Consultation-Liaison (CL) team were assessed to confirm the diagnosis of delirium as per the DSM-IV-TR criteria. [32] Those patients who fulfilled the diagnosis of delirium as per the DSM-IV-TR criteria and whose caregivers provided proxy written informed consent were inducted into the study. This study included all patients aged more than 18 years. However, in this paper only data of geriatric patients is being presented. Data pertaining to the complete study population has been published earlier. [33]

Assessment tools

Delirium rating scale-revised-98 (DRS-R98)

It assesses the symptom frequency by considering as present any item rated as 1 or more. Of the 16 items, 13 comprise the severity scale and 3 are diagnostic items. The severity scale scores range from 0-39, higher scores indicate more severe delirium. DRS-R-98 has been shown to have good interrater reliability and validity. The scale has also been found to have good sensitivity and specificity in distinguishing delirium in mixed neuropsychiatric populations including dementia, depression, and schizophrenia. [34]

Amended delirium motor symptom scale (DMSS)

The Delirium Motor Symptom Scale is used to categorize patients with delirium into various motoric subtypes. DMSS comprises of 11 items, 4 items of identifying hyperactive subtype and 7 items for identifying the hypoactive subtype. [27] In a study done at our centre, amended DMSS was developed. Amended DMSS consists of 13 items (5 hyperactive and 8 hypoactive items), with one item extra for each of the subtyping. [30]

Rating for each item is done on the basis of definite evidence for behaviour in the previous 24 hours, which is a deviation from behaviour prior to onset of delirium. At least 2 out of the 5 hyperactive items and at least 2 out of the 8 hypoactive items must be present for the hyperactive and hypoactive subtypes to be diagnosed respectively. The subtype is considered to be 'mixed' when there is concurrent evidence for both these subtypes and 'no motor subtype' when evidence for neither subtype is present. [27],[30]

Procedure

Caregivers of the patients diagnosed with delirium by the C-L Psychiatry services were approached and they were explained in detail about the nature of the study. Only those patients with confirmed diagnosis of delirium and whose caregivers provided written informed consent were interviewed. The scales were completed on the basis of information obtained from family members, treating team, patients and treatment records. To study the clinical outcome, the patients were followed-up regularly till their discharge from the hospital or death in the hospital.

Data analysis

Statistical Package for Social Scientists, version 14 (SPSS-14) was used for analysis. Statistical analysis involved calculation of frequency counts, percentages, means and standard deviations. Comparisons were done by using chi-square, t-test, ANOVA, Mann-Whitney test, Chi-square with Yate's correction and Fisher exact test as per the requirement.

Results

During the study period 114 cases aged ≥60 years were diagnosed to have delirium. Of these 110 patients could be approached for the study and 98 participated and were included in the final analysis.

As per the amended DMSS, hyperactive subtype (N = 45; 45.9%) was the most common motoric subtype of delirium, followed by hypoactive subtype (N = 23; 23.5%) and mixed subtype (N = 21; 21.4%). One-tenth of patients (N = 9; 9.2%) did not meet the criteria for any of the above 3 subtypes and were categorized as 'no subtype'.

The mean age of the study sample was 70.34 (SD-7.58) years, and majority of them were males (N=67; 68.4%). Delirium was hospital emergent in majority of the patients (N = 67; 68.4%). Only a minority of the patients had comorbid axis-I psychiatric diagnosis (N = 13; 13.3%) and the mean number of medications received by patients at the time of diagnosis of delirium were 4.08 (1.93). Mean duration of delirium at the time of assessment was 4.94 (9.09) days. Most of the patients (N = 85; 86.73%) were treated with psychotropic medications for their delirium and about one-tenth of the patients died during their hospital stay.

There was no significant difference between the 4 motor subtypes on any of these variables (i.e., age, gender, duration of delirium, prevalence of axis-I psychiatric diagnoses, prevalence of dementia, mean number of medications, use of psychotropics for delirium and mortality).

Phenomenology of delirium

On DRS-R-98, all patients fulfilled the diagnostic criteria of 'acute (temporal) onset of symptoms' and, 'presence of an underlying physical disorder'. With regard to other symptoms all patients also had difficulty in attention. In the study sample, majority (>90%) of the patients had disturbances in sleep-wake cycle, orientation and fluctuation of symptoms. The least common symptoms were delusions, visuospatial disturbances and motor retardation [Table 1].

As shown in [Table 1], on comparing the 4 motoric subtypes, significant differences were seen between the various subtypes in the presence of symptoms of perceptual disturbances, delusions, language, thought process abnormality, motor agitation and motor retardation. When the hyperactive group was compared with hypoactive group, significant differences were seen on the presence of symptoms of perceptual disturbances, delusions, thought process abnormality, motor agitation and motor retardation. Of these symptoms, thought process abnormality and motor retardation were significantly more prevalent in patients with hypoactive motoric subtype.

Hyperactive and mixed motoric subtype differed significantly in the symptoms of thought process abnormality and motor retardation. Comparison of mixed subtype and hypoactive subtype revealed significant differences in prevalence of perceptual disturbances, delusions and motor agitation with majority of these being more common in the mixed subtype.

Comparison of severity of symptoms revealed that there were significant differences across the various motoric subtypes for some of the non-cognitive symptoms (DRS-R-98) but the subtypes did not differ in terms of cognitive symptoms as assessed on DRS-R-98 [Table 2].

This is probably the first study from India which has evaluated the motoric subtypes of delirium using standardized validated scales in geriatric population. Most of the previous studies from the West have variously used the descriptions of agitation and retardation from the Memorial Delirium Assessment Scale, [14],[15],[16] Delirium Rating Scale, [17] the Delirium Rating Scale-Revised-98, [18] Richmond agitation/sedation scale, [19] as well as visual analog scales [20] and clinical observation [21] to define motor subtypes. Data also suggests that there is poor concordance among different motor subtypes defined by different approaches to a single population. [29] Further, the previous studies, which have used DMSS to study motoric subtypes of delirium, have been limited to palliative care population. Hence, there is a need to expand the literature and study the delirium subtypes using DMSS/amended DMSS in other patient populations.

The profile of geriatric patients with delirium included in the present study, in terms of mean age and gender distribution, mean number of medications received, frequency of psychotropic medications used for treatment of delirium is similar to the previous study from our centre. [7] The DRS-R-98 profile of the patients included in the present study is also similar to previous study from our centre which reported frequency and severity of various symptoms of delirium in consultation-liaison setting in elderly patients. [7]

Previous studies done in CL psychiatry setup too suggest that hyperactive delirium is the commonest subtype. [35] However, mixed or hypoactive subtypes are reported to be more common in other treatment settings. [9],[31],[36] The difference in prevalence of various subtypes in the CL Psychiatry and other treatment set ups could be due to the inclusion of only referred patients in the CL psychiatry set up in which hypoactive delirium are actually not referred to CL Psychiatry services, [34] in contrast to the studies done in palliative care which have screened all the patients in a particular setting for symptoms of delirium. [31] Taken together these reasons can possibly explain the high prevalence of hyperactive delirium in the present study.

Existing literature suggests that motoric subtypes share core elements of delirium with similar degrees of cognitive impairment. [20],[23],[24] In the present study too no significant difference was observed across the various subtypes of delirum in terms of severity and frequency of cognitive symptoms. Thus, the findings of present study support the observation that delirium is primarily a cognitive disorder.

Findings of the present study also suggest that psychotic symptoms like delusions and hallucinations are more common in hyperactive and mixed subtype compared to hypoactive subtype, which is supported by the previous studies. [25] Similarly, differences in the sleep-wake cycle disturbance, mood lability, language disturbance between different subtypes is supported by previous studies. [6],[18],[24] When the findings of geriatric population as presented in this paper are compared with the adult patients, many similarities were noted in the form of hyperactive delirium being most common subtype, frequency of various symptoms of delirium and relationship of symptoms of delirium with motoric subtypes. These findings suggest that there are no major differences between different age groups. [33]

Conclusion

It can be concluded that hyperactive delirium is the commonest subtype of delirium seen in geriatric patients evaluated in the consultation-liaison services and there is no difference in the frequency and severity of cognitive symptoms across different subtypes of delirium. However, the subtypes do differ from each other on certain non-cognitive symptoms.

Although the present study provides support to important relationships between phenomenology and motoric subtype of delirium, the study has few limitations like inclusion of etiologically heterogeneous sample and carrying out only a single assessment of patients. Further, the study was limited to referrals to a general hospital psychiatry consultation-liaison service and thus may not be generalizable to other populations. The present study included 6 cases with underlying dementia that may have altered the presentation of delirium. Future studies should additionally carryout longitudinal assessment of motoric symptoms and other symptoms of delirum to study their relationship.